The present disclosure relates to a driving device of a synchronous rectification apparatus, and particularly, to a driving device of a synchronous rectification apparatus, which is capable of driving the synchronous rectification apparatus to generate uniform output current regardless of an input voltage in a charging device for charging a low voltage battery.
Low-voltage battery chargers are embedded in eco-friendly vehicles so as to replace generators of engine vehicles. Such a low-voltage battery charger uses energy stored in a high-voltage battery to charge a low-voltage battery having a voltage of about 12 V.
Low-voltage battery chargers have operation characteristics in which conditions such as an input voltage, input current, an output voltage, and output current vary when operating.
Therefore, synchronous rectification apparatuses are being generally used as the low-voltage battery chargers to realize high efficiency having low-voltage high-output current characteristics.
FIG. 1 is a view illustrating a starting device of a synchronous rectification apparatus according to a related art.
Referring to FIG. 1, a driving device of a synchronous rectification apparatus includes a protection part 11 and a comparison part 12.
The driving device of the synchronous rectification apparatus is designed so that the driving device is stopped in operation when an amount of output current is small and operates when load current increases, so as to improve efficiency under a light load and prevent the synchronous rectification apparatus from being damaged due to discontinuous current.
The protection part 11 is configured to protect the synchronous rectification apparatus and is constituted by division resistors.
That is, the protection part 11 includes a first resistor R1 having a first terminal connected to a reference voltage and a second terminal connected to a first terminal of a second resistor R2 and the second resistor R2 having the first terminal connected to the second terminal of the first resistor R1 and a grounded second terminal.
The protection part 11 uses the division resistors to output division resistance values according to an input voltage and the reference voltage. The input voltage represents a voltage inputted into the protection part 11. In detail, the input voltage represents a voltage outputted through a high voltage battery.
The comparison part 12 receives the division resistance value outputted through the protection part 11 into a negative terminal (−) and a command starting value into a positive terminal (+). The comparison part 12 outputs a command value according to a result obtained by comparing the value inputted into the negative terminal to the value inputted into the positive value.
Here, a preset specific command value and output current may be used as the command starting value. On the other hand, the input current may be used as the command starting value when a primary coil of the low-voltage battery charger is controlled.
In the above-described low-voltage battery charger that is designed to control the charging voltage and current of the low voltage battery at the primary coil, it is necessary to correct the command starting value in a case where it is required to accurately control the charging voltage and current when an actual product is embodied due to efficiency, waveform, and duty losses.
Particularly, when a voltage of the high voltage battery which is an input value of the low-voltage battery charger is changed, the input current with respect to the output current may have different values under the same output power to change the starting value of the synchronous rectification apparatus.
When the input voltage increases in a state where the input power is uniform with respect to the predetermined output voltage and output current, it seems that the input current is relatively low. Thus, primary current may operate at a low value.
That is, since the command starting value is set on the basis of the primary current in case of the primary coil control method, the synchronous rectification apparatus operates at a point where the output current is relatively high under the high input voltage than the low input voltage according to the command starting value when the resistors R1 and R2 have consistent values, thereby reducing light load efficiency.
Here, although it is possible to correct command starting value by changing the command starting value, the command starting value needs to be calculated whenever the above-described situations occurs. As a result, time delay occurs, and the command starting value reacts slowly after the voltage of the high battery is converted. Thus, it may be difficult to quickly correct the command starting value.